Emulsions of polyacrylamide, and copolymers of acrylamide with other copolymerizable monomers, which are effective flocculants for many substrates including sewage, cellulose fibers and fines for retention and freeness, metal ore treatment, plating waste, coal trailings, steel mill flue ducts and sinter fines, and potable water have become increasingly important in recent years. These emulsions are usually of the water-in-oil variety and are inverted, by the addition of water thereto, to oil-in-water emulsions during which the polymer is rapidly dissolved in the water. Emulsions and dissolution procedures of this type are disclosed in U.S. Pat. Nos. Re. 28,474, 3,826,771, and 3,284,393, which patents are hereby incorporated herein by reference.
While these emulsions are very effective when used as flocculants, they tend to be materially reduced in their effectiveness when they are subjected to alternating freezing and thawing temperature such as would exist in many areas during the winter season. The repeated temperature cycles tend to cause the emulsions to coagulate, i.e., form into large clumps of polymer rather than remain finely dispersed particles and, as a result, their usefulness as flocculating agents is drastically reduced.